Many automobiles on the road today have various government-mandated devices such as evaporative emission monitoring and control systems. The main purpose for including evaporative emission monitoring and control systems is to reduce the possibility of undesirable emissions from escaping into the atmosphere. A typical evaporative emission control system for a standard internal combustion engine has a filter canister containing activated carbon or charcoal for temporarily storing, trapping or adsorbing fuel vapors emitted from the fuel system when the engine is not running.
Many emission monitoring and control systems also incorporate a fuel vapor leak detection system that specifically monitors the fuel system for undesirable fuel vapor leaks. While somewhat effective, most vapor leak detection systems are typically designed to use a relatively simple two-point analysis for monitoring the pressure differential. Accordingly, a first measurement of the pressure differential is taken and then, a short time later, a second measurement of the pressure differential is taken. These two measurements are compared and the difference, if any, is extrapolated to indicate the presence or absence of a vapor leak in the fuel system. This methodology is somewhat limited, however, by the use of a relatively small sample size. For example, many leak detection systems are subject to noise and various signal spikes. Accordingly, based on the operational environment of the vehicle, the pressure differential may be artificially elevated or depressed at the time of either the first or the second measurement, leading to a false positive result or a false negative result. In either case, the possible inaccuracy of the results may lead to unnecessary repair work or continued operation of a vehicle with an undetected fuel vapor leak.
In view of the foregoing, it should be appreciated that it would be desirable to provide improved equipment and methods for monitoring fuel systems without adding significantly to the cost of the system. Furthermore, additional desirable features will become apparent to one skilled in the art from the foregoing background of the invention and following detailed description of an exemplary embodiment and appended claims.